1. Field of the Invention
The present invention relates to an ink jet recording apparatus including a pivot mechanism that causes an ink cartridge to pivot.
2. Description of the Related Art
A known ink jet recording apparatus includes ink heads that discharge ink onto a recording medium. The ink heads have nozzles for discharging ink. The ink discharged from the nozzles includes process color inks such as cyan ink, magenta ink, yellow ink, and black ink, and spot color inks such as white ink and metallic ink. For example, white ink is used for an underlying layer when printing is performed on the recording medium. Metallic ink is used when a special gloss is imparted to the recording medium. These inks are typically contained in ink packs.
Here, particles of a pigment contained in white ink are larger than particles of a pigment in process color ink, and thus, the pigment is easily deposited. Metallic ink contains metal powder and other substances, and the metal powder and other substances are also easily deposited. That is, among the spot color inks, white ink and metallic ink (hereinafter collectively referred to as “sedimentation ink”) show gradual sedimentation of a pigment or metal powder and other substances in the sedimentation ink with a lapse of a stationary time. When the pigment or the metal powder and other substances in the sedimentation ink are deposited, the concentration of the sedimentation ink in ink packs varies. Specifically, the concentration of the sedimentation ink is low in an upper-layer portion of the ink packs and is high in a lower-layer portion of the ink packs. When the sedimentation ink in this state is supplied to ink heads, a uniform concentration of the sedimentation ink is not discharged from the ink heads, resulting in a failure in obtaining a desired ink concentration. Accordingly, printing quality might degrade. To solve this problem, Japanese Unexamined Patent Application Publication No. 2002-200764, for example, discloses a technique in which an ink pack containing ink is disposed in a specially designed ink cartridge, and the ink cartridge is caused to pivot. With this technique, the ink in the ink pack is agitated and is dispersed in a preferred manner.
Sedimentation of a pigment and metal powder and other substances contained in sedimentation ink tends to progress with time. In the technique described in Japanese Unexamined Patent Application Publication No. 2002-200764, ink in ink packs is agitated by rotating ink cartridges uniformly, and the degree of sedimentation of the pigment and other substances contained in the ink is not taken into consideration. In a case where sedimentation of the pigment and other substances hardly occurs, the ink cartridges only need to be rotated slightly in order to sufficiently disperse the ink in the ink packs. Nevertheless, in the technique described in Japanese Unexamined Patent Application Publication No. 2002-200764, the ink cartridges need to be rotated greatly and uniformly, which causes the problem of lengthening the time necessary for agitation. Elements for sufficiently agitating the ink include a plurality of technical elements such as a rotation speed, a rotation acceleration, the number of rotations, and the manner of rotation (e.g., whether to rotate in one way or rotate in a reciprocating manner) as well as the rotation angle of the ink cartridges. However, there have been no configurations that effectively combine these technical elements to agitate ink sufficiently in a short time.